Antenna Device

Abstract

The antenna device according to the present disclosure comprises: a metal housing (10) having an opening (10a) on one surface thereof and having a liquid crystal display device (40) disposed therein, the liquid crystal display device (40) having a transparent conductive film facing the opening (10a); an antenna conductor (30) transparent to visible light, the antenna conductor having an end face forming a gap serving as a slot line between an edge surrounding the opening (10a) in the metal housing (10) and constituting a composite right-handed / left-handed transmission line in at least a part of the slot line, and causing the composite right-handed / left-handed transmission line in the slot line to function as a leaky wave antenna; and a feeding point (50) disposed in the gap.

Description

[Technical field]

[0001] The present disclosure relates to an antenna device in which a liquid crystal display device having a transparent conductive film over substantially the entire surface of a liquid crystal screen is disposed inside a metal housing. [Background technology]

[0002] Development of transparent antennas using transparent conductive materials with high visible light transmittance is progressing, and Patent Document 1 shows an antenna device in which a liquid crystal display device using an indium tin oxide film as a transparent electrode is placed inside a metal casing. The antenna device disclosed in Patent Document 1 provides a gap between the edge of a transparent antenna and a metal housing, and operates as a slot antenna using the gap as a slot. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7,221,450 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in an antenna device that operates as a slot antenna, with the gap between the edge of the transparent antenna and the metal housing as a slot, the frequency at which the gain is high depends on the size of the metal housing. Therefore, there is a demand for antenna devices that have high gain not only at frequencies of 2.1 GHz, 2.7 GHz, and 3.3 GHz, but also in other frequency bands, such as the 2.4 GHz band used for WI-FI.

[0005] The present disclosure has been made in consideration of the above-mentioned points, and has an object to provide an antenna device that can adjust the frequency at which the gain is high, regardless of the size of the metal housing. [Means for solving the problem]

[0006] The antenna device according to the present disclosure includes a metal housing having an opening on one surface thereof and having a liquid crystal display device having a transparent conductive film facing the opening disposed therein, an antenna conductor that transmits visible light and that forms a gap serving as a slot line between an end face of the metal housing and an edge surrounding the opening, and that constitutes a composite right-handed / left-handed transmission line in at least a part of the slot line, causing the composite right-handed / left-handed transmission line in the slot line to function as a leaky wave antenna, and a feed point disposed in the gap. The antenna conductor has a slit group consisting of a plurality of slits arranged in parallel, whose end faces open in contact with the slot line, and the plurality of slits constitute a left-handed transmission line in the composite right-handed / left-handed transmission line together with a plurality of inductors electrically connected between one side of each of the plurality of slits and the metal casing, and the right-handed transmission line in the composite right-handed / left-handed transmission line exists in the slot line in the region of the antenna conductor where the slit group is formed. Effect of the Invention

[0007] According to the present disclosure, it is possible to obtain high gain over a wide frequency band, regardless of the size of the metal housing. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view of an antenna device according to a first embodiment. [Diagram 2] 2 is a perspective view of a metal housing in the antenna device according to the first embodiment. FIG. [Diagram 3] 2 is a perspective view of the antenna device according to the first embodiment with a protective glass removed. FIG. [Figure 4] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 5] This is an equivalent circuit diagram of a small section of a composite right-handed / left-handed transmission line. [Figure 6] FIG. 11 is an equivalent circuit diagram of a small section of a right-handed transmission line. [Figure 7] FIG. 1 is an equivalent circuit diagram of a small section of a left-handed transmission line. [Figure 8] FIG. 1 is a perspective view showing a slot line model for designing a composite right-handed / left-handed line using a unit cell. [Figure 9] 9 is a cross-sectional view of FIG. 8 taken along line B-B. [Figure 10] FIG. 2 is a plan view showing the configuration of a unit cell. [Figure 11]FIG. 13 is a diagram showing the dispersion characteristics of a unit cell (slit length S1 is 20 mm) illustrating the relationship between frequency and phase change amount. [Figure 12] FIG. 13 is a diagram showing the dispersion characteristics of a unit cell (slit length S1 is 16 mm) illustrating the relationship between frequency and phase change amount. [Figure 13] FIG. 1 is a perspective view showing a slot line model for designing a composite right-handed / left-handed line using 10 unit cells. [Figure 14] This figure shows the electric field distribution when a 4 GHz electromagnetic wave is propagated in a slot line model for designing a composite right-handed / left-handed line using 10 unit cells. [Figure 15] This figure shows the electric field distribution when a 2 GHz electromagnetic wave is propagated in a slot line model for designing a composite right-handed / left-handed line using 10 unit cells. [Figure 16] 4 is a diagram showing frequency characteristics of absolute gain in the zenith direction in the antenna device according to the first embodiment. FIG. [Figure 17] 4 is a diagram showing an absolute gain radiation pattern in the ZY plane at 4 GHz in the antenna apparatus according to the first embodiment. FIG. [Figure 18] 11 is a perspective view of an antenna device of a comparative example with a protective glass removed. FIG. [Figure 19] FIG. 13 is a plan view of the antenna device of the comparative example with the protective glass removed. [Figure 20] 20 is a cross-sectional view taken along CC in FIG. 19 . [Figure 21] 11 is a perspective view of the antenna device according to the second embodiment with a protective glass removed. FIG. [Figure 22] 11 is a perspective view of the antenna device according to the third embodiment with a protective glass removed. FIG. [Figure 23] 13 is a perspective view of the antenna device according to the fourth embodiment with a protective glass removed. FIG. [Figure 24] FIG. 11 is a perspective view of an antenna device according to another embodiment 5 with a protective glass removed. [Diagram 25]13 is a perspective view of the antenna device according to the sixth embodiment with a protective glass removed. FIG. [Figure 26] 13 is an enlarged view of a main part showing an antenna device according to a sixth embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Embodiment 1 The antenna device according to the first embodiment will be described with reference to FIGS. The antenna device according to the first embodiment includes a metal housing 10, a protective glass 20, an antenna conductor 30, a feeding point 50, and a plurality of inductors. The liquid crystal display device includes a liquid crystal display unit 40, which is disposed inside a metal housing 10 of the antenna device.

[0010] As shown in FIGS. 3 and 4, the liquid crystal display device 40 has a transparent electrode 41 on substantially the entire surface of the liquid crystal screen. FIG. 3 is a perspective view with the protective glass 20 removed. The transparent electrode 41 has a rectangular planar shape. A transparent conductive film, which is an indium tin oxide (ITO) film, is used as the transparent electrode 41. In the following description, the transparent electrode 41 will be described as an ITO film 41.

[0011] Since the ITO film 41 has an extremely high sheet resistance of 50 Ω / sq or more, a lossy medium exists directly below the antenna conductor 30 . That is, if a current flows on the ITO film 41, a large loss occurs, and the gain decreases. In the following explanation and illustrations, the liquid crystal display device 40 has various components such as a liquid crystal screen and a backlight, but only the ITO film 41, which is closely related to the antenna conductor 30, i.e., which greatly affects the radiation characteristics of the antenna, is modeled, and other components that make up the liquid crystal display device 40 are omitted.

[0012] 2, the metal housing 10 is a rectangular parallelepiped having an opening 10a on one side, a first side wall 11 to a fourth side wall 14, and a bottom plate 15. Although a rectangular parallelepiped is used as an example, the metal housing 10 does not have to be a rectangular parallelepiped. The first side wall 11 and the second side wall 12 are a pair of opposing long side walls, and the third side wall 13 and the fourth side wall 14 are a pair of opposing short side walls. Opening 10a is located on the top surface of metal housing 10 opposite bottom plate 15, and is rectangular. In the first embodiment, the sides of opening 10a corresponding to first side wall 11 to fourth side wall 14 are referred to as the first side to the fourth side.

[0013] For convenience of explanation, the direction along the third side wall 13 and the fourth side wall 14 is the x-axis, the direction along the first side wall 11 and the second side wall 12 is the y-axis, and the axis perpendicular to the plane of the bottom plate 15 is the z-axis. As shown in FIG. 2, the metal housing 10 has dimensions Cx in the x direction, Cy in the y direction, and Cz in the z direction. That is, the length of the outer surface of each of the third side wall 13 and the fourth side wall 14 is Cx, the length of the outer surface of each of the first side wall 11 and the second side wall 12 is Cy, and the height of each of the first side wall 11 to the fourth side wall 14 is Cz.

[0014] The metal housing 10 has a base 100 and a bezel 110 that constitutes an outer frame integrally bent inward at a right angle from an end face (imaginary plane) of the side wall of the base 100 . The metal housing 10 is made of metal, and the base 100 is a rectangular parallelepiped having a first side wall 11 to a fourth side wall 14 and a bottom plate 15, and the bezel 110 forms a rectangular frame that is integrally bent inward at a right angle from the first side wall 11 to the fourth side wall 14 of the base 100. In the above embodiment, the bezel 110 extends continuously from the base 100 as the metal housing 10. However, the metal housing 10 may be made up of only the base 100 without the bezel 110. Even in the case of metal housing 10 that does not have bezel 110 and is formed only from base body 100, the edges of first side wall 11 to fourth side wall 14 are described as bezel 110 in the first embodiment.

[0015] For convenience of explanation, the bezels 110 will be referred to as a first bezel 111 to a fourth bezel 114 in the following description, corresponding to the first side wall 11 to the fourth side wall 14 . As shown in FIGS. 2 and 4, the width of the edges of first bezel 111 to fourth bezel 114, ie, the edges surrounding opening 10a in metal casing 10, is denoted as Cb. The opening area of ​​the opening 10a of the metal housing 10 is {(Cx-2*Cb)*(Cy-2*Cb)}.

[0016] The protective glass 20 is disposed directly above the opening 10 a of the metal housing 10 . The protective glass 20 serves to protect the liquid crystal display device 40 when the liquid crystal display device 40 is disposed inside the metal housing 10 . Furthermore, on the rear surface of the protective glass 20, that is, on the surface of the liquid crystal display device 40, an antenna conductor 30 which is a transparent conductive film is mounted.

[0017] As shown in FIG. 4, the protective glass 20 is attached to the metal housing 10 with a gap Dg provided between the rear surface of the protective glass 20 and the edge of the bezel 110 of the metal housing 10. As a result, there is also a gap Dg between the end of the antenna conductor 30 and the edge of the bezel 110 of the metal housing 10. A user of the liquid crystal display device views the liquid crystal screen of the liquid crystal display device 40 from the +Z direction to the −Z direction with respect to the protective glass 20, with the protective glass 20 and the antenna conductor 30 interposed therebetween.

[0018] The antenna conductor 30 is a transparent conductive film that transmits visible light. In the first embodiment, a transparent conductive material having a relatively low sheet resistance of 1.5 Ω / sq is used as an example. An end face of the antenna conductor 30 forms a gap serving as a slot line between itself and the edge of a bezel 110 surrounding the opening 10a in the metal housing 10. The antenna conductor 30 serves as one ground plane, the metal housing 10 serves as the other ground plane, and a gap Dm (see FIGS. 3 and 4) between the antenna conductor 30 and the metal housing 10 is used as a slot line.

[0019] The feed point 50 drives power into the antenna conductor 30 . When the antenna conductor 30 is excited with power from the feeding point 50 , high-frequency current flows intensively at the edge of the antenna conductor 30 . As shown in Figures 3 and 4, the power supply point 50 is located between the antenna conductor 30 and the first bezel 111 of the metal housing 10, at a central position of the first bezel 111 of the bezel 110 in the metal housing 10, that is, at a position corresponding to the center of the first side on the first side of the opening 10a of the metal housing 10.

[0020] The feed point 50 is located at the same z coordinate as the antenna conductor 30. In other words, the feed point 50 and the antenna conductor 30 are at the same height relative to the edge of the bezel 110 of the metal housing 10. The power supply point 50 is electrically connected to the bezel 110 of the metal housing 10 by a metal sheet 80 . Therefore, the antenna conductor 30 and the bezel 110 of the metal housing 10 are electrically connected via the feeding point 50 and the metal sheet 80 .

[0021] The excitation of power from the feeding point 50 to the antenna conductor 30 is performed by, for example, an FPC (Flexible Printed Circuit) cable. As shown in FIG. 3, the antenna conductor 30 has a first slit group 31 and a second slit group 32 for forming a composite right / left handed (CRLH) transmission line (hereinafter, CRLH transmission line) in the slot line, on the first side of the opening 10a of the metal housing 10, with respect to the feed point 50.

[0022] The first slit group 31 is made up of a plurality of slits 31a to 31j each having an open end face in contact with a slot line, and the plurality of slits 31a to 31j are arranged in parallel at equal intervals. The transparent conductive film portions of the antenna conductor 30 arranged on both sides of each of the slits 31a to 31j function as a pair of electrodes of a capacitor, and a plurality of capacitors connected in series are formed in the region of the antenna conductor 30 where the first group of slits 31 is formed. In each of the slits 31a to 31j, the slit width Sw is set to 3 mm, and the slit length Sl is set to 20 mm, for example.

[0023] First inductor group 61 and first slit group 31 form a left-handed transmission line in the CRLH transmission line. As shown in FIG. 3, the first inductor group 61 includes a plurality of inductors 61a to 61j electrically connected between one side surface of each of the plurality of slits 31a to 31j in the antenna conductor 30 and the first bezel 111 in the metal casing 10. The multiple inductors 61a to 61j are connected to the antenna conductor 30 in parallel. The inductance of each of the inductors 61a to 61j is set to 10 nH.

[0024] The plurality of slits 31a to 31j in the first slit group 31 and the plurality of inductors 61a to 61j in the first inductor group 61 are arranged alternately and closely adjacent to each other. The slits 31a to 31j and the inductors 61a to 61j connected to one side of the slits 31a to 31j are defined as unit cells, that is, one capacitor and one inductor are defined as a unit cell, and the length of the unit cell including the width of the slit and the width of the inductor in the unit cell is called the period length p, and the period length p is set to 5 mm, for example.

[0025] The equivalent circuit in a small section of the CRLH transmission line is a circuit in which inductors Ls are connected in series, capacitors Cp are connected in parallel, capacitors Cs are connected in series, and inductors Lp are connected in parallel, as shown in FIG. 5. That is, the equivalent circuit in the infinitesimal section of the CRLH transmission line is a circuit that combines the equivalent circuit in the infinitesimal section of the right-handed transmission line in which inductor Ls is connected in series and capacitor Cp is connected in parallel shown in FIG. 6, and the equivalent circuit in the infinitesimal section of the left-handed transmission line in which capacitor Cs is connected in series and inductor Lp is connected in parallel shown in FIG. 7.

[0026] In a slot line with antenna conductor 30 as one ground plane and metal housing 10 as the other ground plane, there is a small section of a right-handed transmission line in which inductor Ls is connected in series and capacitor Cp is connected in parallel in a small section of metal housing 10 and antenna conductor 30. Furthermore, a left-handed transmission line exists by a plurality of series-connected capacitors present in the region of antenna conductor 30 where first slit group 31 is formed and a plurality of inductors 61a to 61j connected in parallel to antenna conductor 30.

[0027] Therefore, a first CRLH transmission line 71 is formed by a region of antenna conductor 30 where first slit group 31 consisting of a plurality of slits 31a to 31j is formed, a first inductor group 61 consisting of a plurality of inductors 61a to 61j, and metal housing 10, and the first slit group 31 and a left-handed transmission line formed by first inductor group 61, and a right-handed transmission line existing in the slot line in the region of antenna conductor 30 where first slit group 31 is formed. First CRLH transmission line 71 is a type of metamaterial, and is a transmission line that exhibits the properties of a right-handed transmission line or a left-handed transmission line depending on the frequency.

[0028] The presence of the first CRLH transmission line 71 makes it possible to function as a leaky wave antenna operating with the first CRLH transmission line 71 in the slot line. The number of the slits 31a to 31j in the first slit group 31 and the number of the inductors 61a to 61j are ten, but they may be two or more.

[0029] The second slit group 32 is made up of a plurality of slits 32a to 32j each having an open end face in contact with a slot line, and the plurality of slits 32a to 32j are arranged in parallel at equal intervals. The transparent conductive film portions of the antenna conductor 30 arranged on both sides of each of the slits 32a to 32j function as a pair of electrodes of a capacitor, and a plurality of capacitors connected in series are formed in the region of the antenna conductor 30 where the second group of slits 32 is formed. In each of the slits 32a to 32j, the slit width Sw is set to 3 mm, and the slit length Sl is set to 20 mm, for example.

[0030] Second inductor group 62 and second slit group 32 form a left-handed transmission line in the CRLH transmission line. The second inductor group 62 includes a plurality of inductors 62a to 62j electrically connected between one side surface of each of the plurality of slits 32a to 32j in the antenna conductor 30 and the first bezel 111 in the metal casing 10, as shown in FIG. The multiple inductors 62a to 62j are connected to the antenna conductor 30 in parallel. The inductance of each of the inductors 62a to 62j is set to 10 nH.

[0031] The plurality of slits 32a to 32j in the second slit group 32 and the plurality of inductors 62a to 62j in the second inductor group 62 are arranged alternately and closely adjacent to each other. The slits 32a to 32j and the inductors 62a to 62j connected to one side of the slits 32a to 32j are defined as unit cells, that is, one capacitor and one inductor are defined as a unit cell, and the periodic length p of the unit cell, including the width of the slits and the width of the inductor in the unit cell, is set to 5 mm, for example.

[0032] A second CRLH transmission line 72 is formed by a region of antenna conductor 30 where second slit group 32 consisting of a plurality of slits 32a-32j is formed, a second inductor group 62 consisting of a plurality of inductors 62a-62j, and metal housing 10, and is composed of a left-handed transmission line formed by second slit group 32 and second inductor group 62, and a right-handed transmission line existing in the slot line in the region of antenna conductor 30 where second slit group 32 is formed. Second CRLH transmission line 72 is a type of metamaterial, and is a transmission line that exhibits the properties of a right-handed transmission line or the properties of a left-handed transmission line depending on the frequency.

[0033] The presence of the second CRLH transmission line 72 allows the second CRLH transmission line 72 to function as a leaky wave antenna operating in a slotline. Although the number of the slits 32a to 32j in the second slit group 32 and the number of the inductors 62a to 62j are ten, they may be any number other than ten as long as they are two or more.

[0034] The planar shape of the antenna conductor 30 including the region where the first slit group 31 is formed and the region where the second slit group 32 is formed (hereinafter simply referred to as the planar shape) is rectangular. When the liquid crystal display device 40 is mounted inside the metal housing 10, the antenna conductor 30 is positioned directly above the ITO film 41, as shown in Figure 4, and the planar shape of the antenna conductor 30 is a rectangle of the same size as the planar shape of the transparent electrode 41. That is, the antenna conductor 30 covers the ITO film 41 .

[0035] Therefore, the ITO film 41 does not exist directly below the magnetic current O, which serves as a radiation source generated in the slot line formed between the end face of the antenna conductor 30 and the edge of the bezel 110 of the metal housing 10 . As a result, the capacitive coupling between the antenna conductor 30 and the ITO film 41 can be suppressed, and the current flowing through the ITO film 41 due to the capacitive coupling can be reduced, making it possible to prevent a decrease in gain.

[0036] Furthermore, the planar shape of the antenna conductor 30 does not have to be the same size as the planar shape of the transparent electrode 41, and the planar shape of the antenna conductor 30 may be larger or smaller than the planar shape of the transparent electrode 41, provided that the gap Dm formed between the end face of the antenna conductor 30 and the edge of the bezel 110 of the metal housing 10 allows a slot line to exist. In short, the planar shape of the antenna conductor 30 may have a planar area that is large enough to allow the gap Dm to exist as a slot line that functions as a leaky wave antenna relative to the opening area of ​​the opening 10a of the metal housing 10.

[0037] Next, the design concept of the antenna device according to the first embodiment will be described. First, a unit cell 700 consisting of one capacitor connected in series and one inductor connected in parallel is constructed with a transparent conductive film 300 corresponding to the antenna conductor 30 having one slit 310 formed therein, and an inductor 610. A slot line model based on a simple CRLH transmission line using the unit cell 700 will be described with reference to Figs. 8 to 10.

[0038] The transparent conductive film 300 is mounted on the surface of the glass 200 which corresponds to the protective glass 20 . The metal film 120 corresponding to the metal housing 10 is mounted on the surface of the glass 200 with one end face provided with a gap Dm between the end face of the transparent conductive film 300 and the metal film 120 . The gap Dm forms a slot line, and the unit cell 700 is disposed at the center of the slot line in the transmission direction. The slit 310 is rectangular and has an open end that contacts the slot line.

[0039] The transparent conductive film portions of the transparent conductive film 300 arranged on both sides of the slit 310 serve as a pair of electrodes connected in series to function as a capacitor. The ITO film 410 corresponding to the ITO film 41 has the same size as the transparent conductive film 300 and is disposed directly above it. The inductor 610 is connected between the transparent conductive film 300 and the metal film 120, and serves as an inductor connected in parallel.

[0040] The slit width Sw was 3 mm, the slit length Sl was 20 mm, the inductance of the inductor 610 was 10 nH, and the periodic length p of the unit cell 700 was 5 mm. In the unit cell 700 constructed in this manner, the dispersion characteristics shown in FIG. 11 were obtained. In Figure 11, the horizontal axis represents frequency, the vertical axis represents the phase change βp before and after an electromagnetic wave passes through unit cell 710, which is the value obtained by multiplying the phase constant β by the periodic length p, the solid line DC1 represents the dispersion characteristics of unit cell 700, which shows the relationship between frequency and phase change, and the dashed line AL is called the AirLine.

[0041] AirLine has a phase velocity of the speed of light (ω = βc, where ω is the angular frequency [rad / s], β is the phase constant [rad / m], and c is the speed of light (≒3×10 8 [m / s]). The region with a smaller phase constant than AirLine (AL) is the fast wave region FWR, and the region with a larger phase constant than AirLine (AL) is the slow wave region SWR. In a band where the dispersion characteristic DC1 is located in the fast wave region FWR, the transmission line in which the slotline unit cell 700 exists operates as a leaky wave antenna. In the band where the dispersion characteristic DC1 is located in the slow wave region SWR, no leakage wave is generated from the transmission line in which the unit cell 700 in the slot line exists.

[0042] As can be seen from the dispersion characteristics of unit cell 700 shown in FIG. 11, a frequency band BR1 around 1.8 GHz and a frequency band BR2 from 3.2 GHz to 4.2 GHz are located in the fast wave region FWR, and the transmission line made of a slot line operates as a leaky wave antenna. Moreover, the band BR3 where the phase shift βp is 0, and the band between bands BR1 and BR2 in FIG. 11, is a bandgap region, which is a region where electromagnetic waves do not propagate through the transmission line in which the unit cell 700 of the slot line exists.

[0043] Next, in the unit cell 700, the slit length Sl was changed from 20 mm to 16 mm, and the dispersion characteristics of the unit cell 700 were examined, and the results shown in FIG. 12 were obtained. The slit width Sw is 3 mm, the inductance of the inductor 610 is 10 nH, and the periodic length p of the unit cell 700 is 5 mm, which is the same as the unit cell 700 having a slit length Sl of 20 mm. In FIG. 12, a solid line DC1 indicates the dispersion characteristics of a unit cell 700 with a slit length Sl of 20 mm, and a dashed line DC2 indicates the dispersion characteristics of a unit cell 700 with a slit length Sl of 16 mm.

[0044] As can be seen from the dispersion characteristics of unit cell 700 shown in FIG. 12, the frequency band BR4 of 4.3 GHz to 5 GHz is located in the fast wave region FWR, and the transmission line in which unit cell 700 exists in the slot line operates as a leaky wave antenna. Therefore, the slit length Sl may be set to 20 mm for the electromagnetic wave frequency band BR1 around 1.8 GHz and the electromagnetic wave frequency band BR2 of 3.2 GHz to 4.2 GHz, and the slit length Sl may be set to 16 mm for the electromagnetic wave frequency band BR4 of 4.3 GHz to 5 GHz.

[0045] The slit lengths Sl shown are 20 mm and 16 mm. By changing the slit length Sl, the frequency band in which it operates as a leaky wave antenna can be changed, and the transmission line consisting of a slot line can be used as a leaky wave antenna for various frequency bands. That is, an antenna device that is suited to the frequency band of electromagnetic waves can be obtained by adjusting the slit length Sl.

[0046] Although it has been stated above that the frequency band in which the leaky wave antenna operates can be changed by changing the slit length Sl, the capacitance value of the unit cell 700 can also be changed by changing the slit width Sw, so that an antenna device that can be matched to the frequency band of electromagnetic waves can be obtained by changing the length of the slit width Sw. Similarly, an antenna device adapted to the frequency band of electromagnetic waves can be obtained by adjusting the inductance of the inductor 610 of the unit cell 700.

[0047] When the slot line is operated as a leaky wave antenna using only one unit cell 700, the amount of electromagnetic wave leakage is small. Therefore, it is preferable to arrange multiple unit cells 700 to increase the amount of leakage of electromagnetic waves propagating through the slot line. Figure 13 shows a slot line model using a CRLH transmission line with 10 unit cells arranged. The slot line model shown in FIG. 13 is a slot line model based on a CRLH transmission line in which ten unit cells shown in FIGS. 8 to 10 are arranged in parallel along the slot line.

[0048] The transparent conductive film 300 has a slit group 310 consisting of ten slits 310a to 310j, each of which is in contact with a slot line and has an open end face. The ten inductors 610a to 610j electrically connected between one side surface of each of the ten slits 310a to 310j in the transparent conductive film 300 and the metal film 120 constitute a first inductor group 61.

[0049] The ten slits 310a to 310j and the ten inductors 610a to 610j in the slit group 310 are arranged alternately and closely adjacent to each other. Therefore, a CRLH transmission line 710 having ten unit cells 700 is formed by the region of the transparent conductive film 300 in which the slit group 310 is formed and the ten inductors 610a to 610j.

[0050] In the CRLH transmission line 710 having ten unit cells 700 thus configured, similarly to the dispersion characteristics of one unit cell 700 (see FIG. 11), the frequency band BR1 around 1.8 GHz and the frequency band BR2 of 3.2 GHz to 4.2 GHz are located in the fast wave region FWR, the transmission line made of a slot line operates as a leaky wave antenna, and the band between bands BR1 and BR2 is a bandgap region.

[0051] In the CRLH transmission line 710 having ten unit cells 700 configured in this manner, FIG. 15 shows the electric field distribution when a 4 GHz electromagnetic wave is propagated in the direction from the + direction to the - direction of the x-axis shown in FIG. 13, with the transmission line having ten unit cells 700 in a slot line operating as a leaky wave antenna. FIG. 14 shows the electric field distribution when an electromagnetic wave of 2 GHz, which is in the band gap region, is propagated.

[0052] As can be seen from FIG. 14, it can be confirmed that electromagnetic waves leak into space in the CRLH transmission line 710 having ten unit cells 700. Moreover, as can be seen from FIG. 15, in the CRLH transmission line 710 having ten unit cells 700, it can be confirmed that the electromagnetic waves do not leak and do not propagate beyond the CRLH transmission line 710.

[0053] Next, a test result of the gain versus frequency in the antenna device according to the first embodiment will be described. In the antenna apparatus according to the first embodiment, each of the first CRLH transmission line 71 and the second CRLH transmission line 72 has the same design as the CRLH transmission line 710 having ten unit cells 700 shown in FIG. In the antenna device of embodiment 1, the absolute gain in the zenith direction (+z direction) versus frequency, which is a verification result, is shown by a solid line G in FIG. 16, and the absolute gain radiation pattern in the vertical plane (zy plane) is shown by a solid line G in FIG.

[0054] For reference, the absolute gain in the zenith direction (+z direction) versus frequency, which is the verification result in the comparative example shown in Figures 18 to 20, is shown by dashed line R in Figure 16, and the absolute gain radiation pattern in the vertical plane (zy plane) is shown by dashed line R in Figure 17. The antenna device of the comparative example is shaped so that the antenna conductor 30R covers the ITO film 41R, and utilizes a magnetic current O generated in a gap Dm between the antenna conductor 30R and a bezel 110R (111R to 114R) of a metal housing 10R.

[0055] That is, the antenna device of the comparative example has the following configuration. The metal housing 10R has an opening 10a on one side, is a rectangular parallelepiped having a first side wall 11 to a fourth side wall 14 and a bottom plate 15, and has a bezel 110R (111R to 114R) that forms an outer frame. The antenna conductor 30R is mounted on the rear surface of the protective glass 20R and is a rectangular transparent conductive film. The antenna conductor 30R is disposed directly above a rectangular ITO film 41R provided on the liquid crystal screen of the liquid crystal display device.

[0056] The antenna conductor 30R and the ITO film 41R have the same shape and size. The antenna device of the comparative example does not have the first CRLH transmission line 71 and the second CRLH transmission line 72 in embodiment 1, that is, the antenna conductor 30R has the same shape except that it does not have the first slit group 31 and the second slit group 32 and the first inductor group 61 and the second inductor group 62.

[0057] As can be seen from the solid line G in Fig. 16, the antenna device according to the first embodiment has a higher absolute gain in the zenith direction than the antenna device of the comparative example (dashed line R) in the band BR2 of 3.2 GHz to 4.2 GHz. The reason that the absolute gain in the zenith direction is high is that the first CRLH transmission line 71 and the second CRLH transmission line 72 operate as leaky wave antennas, resulting in an increased gain.

[0058] Furthermore, as can be seen from the solid line G in FIG. 17, the antenna device according to the first embodiment has an increased absolute gain in the front direction at a frequency of 4 GHz compared to the antenna device of the comparative example (dashed line R). In this way, the antenna device according to the first embodiment has a high absolute gain in the zenith direction in the wide frequency band BR2 of 3.2 GHz to 4.2 GHz without changing the size of the metal housing, and can be applied to a wide range of applications.

[0059] In addition, in the antenna device of embodiment 1, if the slit length Sl is set to 16 mm, it is possible to obtain a high absolute gain in the zenith direction in the 4.3 GHz to 5 GHz band BR4 in which the antenna device operates as a leaky wave antenna as described using Figure 12.

[0060] As described above, the antenna device of the first embodiment has antenna conductor 30 which forms gap Dm serving as a slot line between itself and the edge surrounding opening 10a in metal housing 10, and a composite right-handed / left-handed transmission line is formed in at least a part of the slot line, and the composite right-handed / left-handed transmission line in the slot line is made to function as a leaky wave antenna. Therefore, high gain can be obtained over a wide frequency band regardless of the size of metal housing 10, and the range of applications is expanded.

[0061] Furthermore, the antenna device according to the first embodiment has a plurality of slits 31a to 31j, 32a to 32j arranged in parallel, with their end faces opening in contact with the gap Dm, in the antenna conductor 30 which forms a gap Dm between the edge surrounding the opening 10a in the metal casing 10 and the antenna conductor 30, and is provided with a plurality of inductors 61a to 61j which are electrically connected between one side surface of each of the plurality of slits 31a to 31j, 32a to 32j in the antenna conductor 30 and the metal casing 10. This makes it possible to obtain a high gain over a wide frequency band regardless of the size of the metal casing 10, and by changing at least one of the slit length Sl and slit width Sw of each of the slits 31a to 31j, 32a to 32j, or the inductance of the inductors 61a to 61j, the frequency band with high gain can be changed regardless of the size of the metal casing 10, thereby further expanding the range of applications.

[0062] Embodiment 2 The antenna device according to the second embodiment will be described with reference to FIG. In the antenna device of embodiment 1, the first CRLH transmission line 71 and the second CRLH transmission line 72 are arranged on the same side of the opening 10a of the metal housing 10 as the side of the opening 10a on which the feed point 50 is arranged, that is, on the side of the first side wall 11 of the metal housing 10.

[0063] In contrast, in the antenna device according to the second embodiment, the third CRLH transmission line 73 and the fourth CRLH transmission line 74 are arranged on the side of the opening 10a that faces the side of the opening 10a of the metal housing 10 on which the feed point 50 is arranged, that is, on the side of the second side wall 12 of the metal housing 10. Other points of the antenna device according to the second embodiment are the same as those of the antenna device according to the first embodiment. In FIG. 21, the same reference numerals as those in FIGS. 1 to 4 designate the same or corresponding parts.

[0064] The following description will focus on the differences from the antenna device according to the first embodiment. The third CRLH transmission line 73 is disposed on the third bezel 113 side of the metal housing 10 . The third CRLH transmission line 73 is composed of the region of the antenna conductor 30 in which the third slit group 33 is formed and a plurality of inductors 63a to 63j.

[0065] The third slit group 33 is made up of a plurality of slits 33a to 33j each having an open end face in contact with a slot line on the second bezel 112 side of the metal casing 10, and the plurality of slits 33a to 33j are arranged in parallel at equal intervals. The number of the slits 33a to 33j is, for example, 10, and the slit width Sw and slit length Sl of each of the slits 33a to 33j are, for example, 3 mm and 20 mm, respectively.

[0066] The third inductor group 63 includes a plurality of inductors 63a to 63j electrically connected between one side surface of each of the plurality of slits 33a to 33j in the antenna conductor 30 and the second bezel 112 of the metal housing . The multiple inductors 63a to 63j are connected to the antenna conductor 30 in parallel. The number of the inductors 63a to 63j is, for example, 10, and the inductance of each of the inductors 63a to 63j is set to 10 nH.

[0067] The fourth CRLH transmission line 74 is disposed on the fourth bezel 114 side of the metal housing 10 . The third CRLH transmission line 73 and the fourth CRLH transmission line 74 are arranged symmetrically with respect to the center point in the longitudinal direction of the second bezel 112 of the metal housing 10, that is, in the y-axis direction. The fourth CRLH transmission line 74 is composed of the region of the antenna conductor 30 in which the fourth slit group 34 is formed and the multiple inductors 64a to 64j.

[0068] The fourth slit group 34 is made up of a plurality of slits 34a to 34j each having an open end face in contact with a slot line on the second bezel 112 side of the metal housing 10, and the plurality of slits 34a to 34j are arranged in parallel at equal intervals. The number of the slits 34a to 34j is, for example, 10, and the slit width Sw and slit length Sl of each of the slits 34a to 34j are, for example, 3 mm and 20 mm, respectively.

[0069] The fourth inductor group 64 includes a plurality of inductors 64a to 64j electrically connected between one side surface of each of the plurality of slits a to j in the antenna conductor 30 and the second bezel 112 of the metal housing . The multiple inductors 64a to 64j are connected to the antenna conductor 30 in parallel. The number of the inductors 64a to 64j is, for example, 10, and the inductance of each of the inductors 64a to 64j is 10 nH. The antenna device according to the second embodiment has the same effects as the antenna device according to the first embodiment.

[0070] Embodiment 3 An antenna device according to the third embodiment will be described with reference to FIG. In the antenna device of embodiment 1, the first CRLH transmission line 71 and the second CRLH transmission line 72 are arranged on the same side of the opening 10a of the metal housing 10 as the side of the opening 10a on which the feed point 50 is arranged, that is, on the side of the first side wall 11 of the metal housing 10.

[0071] In contrast, in the antenna device according to the third embodiment, the fifth CRLH transmission line 75 and the sixth CRLH transmission line 76 are each arranged on the side of the opening 10a that is perpendicular to the side of the opening 10a of the metal housing 10 on which the feed point 50 is arranged, that is, on the third side wall 13 side and the fourth side wall 14 side of the metal housing 10. Other points of the antenna device according to the third embodiment are the same as those of the antenna device according to the first embodiment. In FIG. 22, the same reference numerals as those in FIGS. 1 to 4 denote the same or corresponding parts.

[0072] The following description will focus on the differences from the antenna device according to the first embodiment. The fifth CRLH transmission line 75 is disposed at the center of the third bezel 113 of the metal housing 10 in the longitudinal direction. The fifth CRLH transmission line 75 is composed of the region of the antenna conductor 30 in which the fifth slit group 35 is formed and a plurality of inductors 65a to 65j.

[0073] The fifth slit group 35 is made up of a plurality of slits 35a to 35j each having an open end face in contact with a slot line on the third bezel 113 side of the metal casing 10, and the plurality of slits 35a to 35j are arranged in parallel at equal intervals. The number of the slits 35a to 35j is, for example, 10, and the slit width Sw and slit length Sl of each of the slits 35a to 35j are, for example, 3 mm and 20 mm, respectively.

[0074] The fifth inductor group 65 includes a plurality of inductors 65a to 65j electrically connected between one side surface of each of the plurality of slits a to j in the antenna conductor 30 and the third bezel 113 of the metal casing . The multiple inductors 65a to 65j are connected to the antenna conductor 30 in parallel. The number of the inductors 65a to 65j is, for example, 10, and the inductance of each of the inductors 65a to 65j is 10 nH.

[0075] The sixth CRLH transmission line 76 is disposed at the center in the longitudinal direction of the metal housing 10 on the fourth bezel 114 side. The sixth CRLH transmission line 76 is composed of the region of the antenna conductor 30 in which the sixth slit group 36 is formed and a plurality of inductors 66a to 66j.

[0076] The sixth slit group 36 is made up of a plurality of slits 36a to 36j each having an open end face in contact with a slot line on the fourth bezel 114 side of the metal casing 10, and the plurality of slits 36a to 36j are arranged in parallel at equal intervals. The number of the slits 36a to 36j is, for example, 10, and the slit width Sw and slit length Sl of each of the slits 36a to 36j are, for example, 3 mm and 20 mm, respectively.

[0077] The sixth inductor group 66 includes a plurality of inductors 66a to 66j electrically connected between one side surface of each of the plurality of slits a to j in the antenna conductor 30 and the fourth bezel 114 of the metal housing . The multiple inductors 66a to 66j are connected to the antenna conductor 30 in parallel. The number of the inductors 66a to 66j is, for example, 10, and the inductance of each of the inductors 66a to 66j is 10 nH. The antenna device according to the third embodiment has the same effects as the antenna device according to the first embodiment.

[0078] Embodiment 4 An antenna device according to the fourth embodiment will be described with reference to FIG. In the antenna device of embodiment 1, the first CRLH transmission line 71 and the second CRLH transmission line 72 are arranged on the same side of the opening 10a of the metal housing 10 as the side of the opening 10a on which the feed point 50 is arranged, that is, on the side of the first side wall 11 of the metal housing 10.

[0079] In contrast, in the antenna device of embodiment 4, in addition to the first CRLH transmission line 71 and the second CRLH transmission line 72, a fifth CRLH transmission line 75 and a sixth CRLH transmission line 76 are each arranged on the side of the opening 10a that is perpendicular to the side of the opening 10a of the metal housing 10 on which the feed point 50 is arranged, that is, on the third side wall 13 side and the fourth side wall 14 side of the metal housing 10.

[0080] That is, the antenna apparatus according to the fourth embodiment has a first CRLH transmission line 71, a second CRLH transmission line, a fifth CRLH transmission line 75, and a sixth CRLH transmission line . Other points of the antenna device according to the fourth embodiment are the same as those of the antenna device according to the first embodiment. In FIG. 23, the same reference numerals as those in FIGS. 1 to 4 denote the same or corresponding parts.

[0081] The fifth CRLH transmission line 75 and the sixth CRLH transmission line 76 are the same as the fifth CRLH transmission line 75 and the sixth CRLH transmission line 76 in the antenna device according to the third embodiment. The antenna device according to the fourth embodiment has the same effects as the antenna device according to the first embodiment.

[0082] Embodiment 5. The antenna device according to the fifth embodiment will be described with reference to FIG. In the antenna device of embodiment 1, the first CRLH transmission line 71 and the second CRLH transmission line 72 are arranged on the same side of the opening 10a of the metal housing 10 as the side of the opening 10a on which the feed point 50 is arranged, that is, on the side of the first side wall 11 of the metal housing 10.

[0083] In contrast, in the antenna device of embodiment 5, in addition to the first CRLH transmission line 71 and the second CRLH transmission line 72, a third CRLH transmission line 73 and a fourth CRLH transmission line 74 are arranged on the side of the opening 10a of the metal housing 10 that faces the side of the opening 10a where the feed point 50 is arranged, that is, on the second side wall 12 side of the metal housing 10, and a fifth CRLH transmission line 75 and a sixth CRLH transmission line 76 are arranged on the side of the opening 10a that is perpendicular to the side of the opening 10a of the metal housing 10 where the feed point 50 is arranged, that is, on the third side wall 13 side and the fourth side wall 14 side of the metal housing 10.

[0084] That is, the antenna device according to embodiment 5 has a first CRLH transmission line 71 and a second CRLH transmission line, a third CRLH transmission line 73 and a fourth CRLH transmission line 74, and a fifth CRLH transmission line 75 and a sixth CRLH transmission line 76. In the antenna device according to the fifth embodiment, CRLH transmission lines 71 to 74 are arranged on all four sides of an opening 10a of a metal housing 10. Other points of the antenna device according to the fifth embodiment are the same as those of the antenna device according to the first embodiment. In FIG. 24, the same reference numerals as those in FIGS. 1 to 4 indicate the same or corresponding parts.

[0085] The third CRLH transmission line 73 and the fourth CRLH transmission line 74 are the same as the third CRLH transmission line 73 and the fourth CRLH transmission line 74 in the antenna device according to the second embodiment. The fifth CRLH transmission line 75 and the sixth CRLH transmission line 76 are the same as the fifth CRLH transmission line 75 and the sixth CRLH transmission line 76 in the antenna device according to the third embodiment. The antenna device according to the fifth embodiment has the same effects as the antenna device according to the first embodiment.

[0086] Embodiment 6 An antenna device according to the sixth embodiment will be described with reference to FIGS. The antenna device according to the sixth embodiment differs from the antenna device according to the first embodiment in that a meander element is used as an inductor, but other points are the same as the antenna device according to the first embodiment. 25 and 26, the same reference numerals as those in FIGS. 1 to 4 denote the same or corresponding parts.

[0087] The following description will focus on the differences from the antenna device according to the first embodiment. In the antenna device of embodiment 6, the seventh CRLH transmission line 77 and the eighth CRLH transmission line 78 are arranged on the same side of the opening 10a of the metal housing 10 as the side of the opening 10a on which the feed point 50 is arranged, that is, on the side of the first side wall 11 of the metal housing 10. The seventh CRLH transmission line 77 is disposed on the third bezel 113 side of the metal housing 10 . The seventh CRLH transmission line 77 is composed of the region of the antenna conductor 30 in which the seventh slit group 37 is formed and a plurality of inductors 67a to 67e.

[0088] The seventh slit group 37 is made up of a plurality of slits 37a to 37e each having an open end face in contact with a slot line on the first bezel 111 side of the metal casing 10, and the plurality of slits 37a to 37e are arranged in parallel at equal intervals. The number of the slits 37a to 37e is, for example, five.

[0089] The seventh inductor group 67 includes a plurality of inductors 67a to 67e electrically connected between one side surface of each of the plurality of slits 37a to 37e in the antenna conductor 30 and the first bezel 111 of the metal housing . The multiple inductors 67a to 67e are connected to the antenna conductor 30 in parallel. Each of the inductors 67a to 67e is a meander element. The number of the inductors 67a to 67e is, for example, five.

[0090] The eighth CRLH transmission line 78 is disposed on the fourth bezel 114 side of the metal housing 10 . The seventh CRLH transmission line 77 and the eighth CRLH transmission line 78 are arranged symmetrically with respect to the center point in the longitudinal direction of the first bezel 111 of the metal housing 10, that is, in the y-axis direction. The eighth CRLH transmission line 78 is composed of the region of the antenna conductor 30 in which the eighth slit group 38 is formed and a plurality of inductors 68a to 68e.

[0091] The eighth slit group 38 is made up of a plurality of slits 38a to 38e, each of which has an open end face in contact with the slot line on the first bezel 111 side of the metal casing 10, and the plurality of slits 38a to 38e are arranged in parallel at equal intervals. The number of the slits 38a to 38e is, for example, five.

[0092] The eighth inductor group 68 includes a plurality of inductors 68a to 68e electrically connected between one side surface of each of the plurality of slits a to e in the antenna conductor 30 and the first bezel 111 of the metal housing . The multiple inductors 68a to 68e are connected to the antenna conductor 30 in parallel. Each of the inductors 68a to 68e is a meander element. The number of the inductors 68a to 68e is, for example, five.

[0093] The antenna device according to the sixth embodiment has the same effects as the antenna device according to the first embodiment, and in addition, since a meander element is used as an inductor, the number of elements serving as an inductor can be reduced.

[0094] It should be noted that the embodiments may be freely combined, or any of the components in each embodiment may be modified, or any of the components in each embodiment may be omitted. [Industrial Applicability]

[0095] The antenna device according to the present disclosure is applied to an antenna device that uses an antenna conductor that transmits visible light, and is applied to a liquid crystal display device in which a liquid crystal display device is disposed inside a metal housing. [Explanation of symbols]

[0096] 10 metal housing, 10a opening, 20 protective glass, 30 antenna conductor, 31-37 slit group, 31a-31j, 32a-32j, 33a-33j, 34a-34j, 35a-35j, 36a-36j, 37a-37e, 38a-38e slit, 40 liquid crystal display device, 41 transparent electrode (ITO film), 50 power supply point, 61-68 inductor group, 61a-61j, 62a-62j, 63a-63j, 64a-64j, 65a-65j, 66a-66j, 67a-67e, 68a-68e inductor, 71-78 CRLH transmission line.

Claims

1. a metal housing having an opening on one side thereof and a liquid crystal display device having a transparent conductive film facing the opening therein; an antenna conductor that is transparent to visible light, the antenna conductor having an end face that forms a gap serving as a slot line between an edge surrounding the opening in the metal housing, the end face forming a composite right-handed / left-handed transmission line in at least a part of the slot line, and causing the composite right-handed / left-handed transmission line in the slot line to function as a leaky wave antenna; A feed point disposed in the gap; Equipped with the antenna conductor has an end face that opens in contact with the slot line and includes a slit group made up of a plurality of slits arranged in parallel, a plurality of inductors electrically connected between one side surface of each of the plurality of slits and the metal housing constitute a left-handed transmission line in the composite right-handed / left-handed transmission line, a right-handed transmission line of the composite right-handed / left-handed transmission line is present in a slot line in a region of the antenna conductor in which the group of slits is formed; Antenna device.

2. The antenna device according to claim 1 , wherein the feed point is disposed at the center of one side of the opening of the metal housing.

3. The antenna device according to claim 1 , wherein the metal housing has a wide bezel around its edge that surrounds the opening.

4. The antenna device according to claim 1 , wherein each of the plurality of inductors is a meander-shaped element.

5. 5. The antenna device according to claim 1, wherein the opening of the metal housing is rectangular, and the plurality of slits and the plurality of inductors are arranged on the same side of the opening as the side of the opening of the metal housing on which the power supply point is arranged.

6. 6. The antenna device according to claim 5, wherein the plurality of slits and the plurality of inductors are each divided into two groups, and the divided groups are arranged symmetrically with respect to the feed point.

7. 5. The antenna device according to claim 1, wherein the opening of the metal housing is rectangular, and the plurality of slits and the plurality of inductors are arranged on a side of the opening opposite to the side of the opening of the metal housing on which the power supply point is arranged.

8. 5. The antenna device according to claim 1, wherein the opening of the metal housing is rectangular, and the plurality of slits and the plurality of inductors are arranged on a side of the opening that is perpendicular to the side of the opening of the metal housing on which the power supply point is arranged.

9. a metal housing having an opening on one side thereof and a liquid crystal display device having a transparent conductive film facing the opening therein; an antenna conductor that transmits visible light, the antenna conductor having an end face disposed with a gap between the end face and an edge surrounding the opening in the metal housing, the end face having a plurality of slits arranged in parallel and opening in contact with the gap; a plurality of inductors electrically connected between one side surface of each of the plurality of slits in the antenna conductor and the metal housing; A feed point disposed in the gap; An antenna device comprising: